Although many variations of high speed recording tape guides, including air guides, are known and used in the magnetic recording industry, it has been found that a number of serious problems relating to friction and tape alignment have been associated with their use. These problems become particularly acute when processing video signals due to the high tape speeds involved and, consequently, the multiplicity of tracks of extremely narrow width that must be utilized in order to provide record and/or playback capability for programs of reasonable duration on a tape of manageable length.
For example, in a video system which operates at a tape speed of 120 inches per second, 36,000 feet of tape pass the transducing head each hour. Due to physical and cost limitations in reel size, the data is generally recorded on a multiplicity of parallel tracks, and the shorter length of tape which results is passed repeatedly past the transducer head, each time reading information from a different track. In this manner an 1800 foot reel of tape having 30 tracks can be used to record or playback a 90 minute program utilizing the above-described system.
However, the requirement that the tape pass through the transport 30 times per program has resulted in serious wear considerations which it has been found may be greatly overcome through utilization of air guide type of tape transport. In addition, due to the requirement that 30 different informational tracks be placed in parallel relation on a tape of reasonable and economical width for consumer use, typically 1/4 inch, a related problem concerning alignment of the extremely narrow tracks on the tape with a corresponding transducer head has arisen. This problem is compounded by the fact that commercially available magnetic tape is manufactured to width tolerances which approach the individual track width required (typically about 6 mil with 2 mil spacing between tracks) for utilization of 30 tracks on a 1/4 inch tape format.
Conventional tape guides have attempted to control tape track to head alignment by providing vertical guide flanges on opposite sides of the path followed by the tape as it is transported past the head. However, it has been found that particularly in high speed applications, a minimum clearance must be provided between the tape and guide flanges to reduce friction. Furthermore, any non-straightness of the tape over the length of the guide requires additional clearance between the tape and guide flanges. These clearance requirements inhibit accurate tape guidance as any lateral shift of the tape within the guide flange area will result in guidance error, since the playback head contact pattern will not precisely duplicate the record head pattern recorded as a track on the tape. It has also been found that the rubbing of the tape along conventional guide flanges produces undesirable longitudinal vibrations in the tape, commonly referred to as "scrape flutter", which degrade the overall performance of the video system.